Problem: $ E = \left[\begin{array}{rrr}2 & 2 & 0 \\ 0 & 1 & 0 \\ 2 & 0 & 2\end{array}\right]$ What is $ E^{-1}$ ?
$ = \left[\begin{array}{rrr}\frac{1}{2} & -1 & 0 \\ 0 & 1 & 0 \\ -\frac{1}{2} & 1 & \frac{1}{2}\end{array}\right]$